1. Field of the Invention
The present invention relates to a roller chain for a linear guideway, and more particularly to prevent the indirect impact between two neighboring rollers caused by the spacer therebetween, thus substantially reducing the impact-caused noise.
2. Description of the Prior Art
The existing linear guideway essentially comprises a rail and a slide block. The rail is an elongated structure defined with rolling grooves for allowing the rollers to circulate therein. The slide block is reverse U-shaped and also defined with grooves for cooperating with the rolling grooves. And two end caps are installed at both ends of the slide block to enable the rollers to circulate. Each of the end caps is defined with a return path for enabling the rollers to circulate from the slide block to the rail.
The existing technologies for the roller chain are generally classified into the following categories:
First, JP Pat. No. 11-344033 discloses a roller chain as shown in FIGS. 1a-1d, the roller chain 5 comprises a plurality spacers 11, and the spacers 11 are in arc-shaped surface-to-surface contact with the rollers 3. This roller chain has the following problems:
1. Indirect impact will be caused between neighboring rollers 3 via the spacers 11.
2. The spacers 11 are in surface-to-surface contact with the rollers 3, so that the friction of the chain 12 with respect to the roller 3 is increased, and so is the rolling resistance thereof.
3. The roller chain 12 itself doesn't have enough space to reserve lubricant.
4. The roller chain is made by using the rollers 3 as a core in injection molding process, and the rollers 3 must be put in the mold before the forming the roller chain. Therefore, making such a roller chain is laboursome and time-consuming.
Second, U.S. Pat. No. 6,070,479 discloses a roller chain as shown in FIG. 2, wherein the spacers 6 are formed at both sides of the respective rollers 70, each of the links 5 defines a receiving hole 4, and the spacers 6 are connected by the connecting portions 5a. 
The disadvantages of this kind of roller chain are explained below:
1. Indirect impact will be caused between neighboring rollers 70 via the connecting portions 5a. 
2. The contacting area of the spacers 6 with respect to the rollers 70 is large, thus increasing the rolling resistance.
3. The roller chain itself doesn't have enough space to reserve lubricant.
4. It is very difficult to manufacture such a roller chain structure.
U.S. Pat. No. 6,203,200 discloses another roller chain as shown in FIGS. 3a-3c, wherein the roller chain is provided with a plurality of retaining portions 21 for retaining both ends 20 of the respective rollers, and a spacer 18 is arranged between each two neighboring rollers 13a. 
The disadvantages of this kind of roller chain are explained below:
1. Indirect impact will be caused between neighboring rollers 13a by the spacer 18.
2. both ends 20 of the rollers are drilled with holes 16, and this will not only increase the production cost but will reduce the strength of the rollers 13a. 
3. The roller chain itself doesn't have enough space to reserve lubricant.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.